Tire Tread Comprising Wavy Grooves and Sipes

Abstract

Tread with longitudinally oriented grooves ( 31, 41, 42 ) at least one is wavy ( 31 ) opening onto tread surface ( 10 ), at least one rib ( 21 ) oriented in the longitudinal direction and delimited by ( 31 ) with external cavities ( 311 ) opening to tread surface and internal cavities ( 312 ) hidden within the thickness of the tread, cavities ( 311 ) opening onto the surface ( 10 ) when new with a contour ( 310 ) having farthest-spaced endpoints A and B separated by a distance Lm, the rib ( 21 ) of width Ln having transverse sipes ( 5 ), made at a mean pitch Pi, where the length Lm of contour ( 310 ) of cavity ( 311 ) is equal to or greater than an integer multiple N of the pitch Pi times an amount at most equal to 25% of this integer multiple N of the pitch Pi, when new, N+1 transverse sipes ( 5 ) of rib ( 21 ) open into cavity ( 311 ) bordering the rib.

1 . A tire tread comprising a tread surface, a thickness of material to be worn away during running, this tread being provided with a tread pattern formed by at least two longitudinally oriented grooves opening onto the tread surface of the tread, and of which at least one is a wavy groove, this tread comprising at least one rib oriented in the longitudinal direction of the tread and delimited by said at least one wavy groove, each wavy groove comprising external cavities opening onto the tread surface and internal cavities hidden within the thickness of the tread, the external cavities of each wavy groove opening onto the tread surface when new with a contour of which the longitudinally farthest-spaced endpoints (A, B) are separated by a longitudinal distance Lm, this distance Lm measuring the maximum longitudinal length of the contour of each external cavity, each external cavity having a depth Ho, the rib of width Ln comprising a plurality of transverse sipes, which is to say sipes oriented at 45 degrees or more to the longitudinal direction, made at a mean pitch Pi, the depth of these transverse sipes being at least equal to the depth Ho of the external cavities of the wavy groove delimiting said rib, wherein:
 the longitudinal length Lm of the contour of the external cavity is equal to or greater than an integer multiple N of the pitch Pi times an amount at most equal to 25% of this integer multiple N of the pitch Pi,   when new, N+1 transverse sipes of the one same rib open into each open cavity bordering said rib, one of these transverse sipes opening near the end point A of the contour ( 310 ) at a distance D 1  from this point A, another transverse sipe opening near the other end point B of the contour at a distance D 2  from this point B, the difference between the two distances D 1  and D 2  being at most equal to 5 mm.   
     
     
         2 . The tread according to  claim 1 , wherein the total voids volume ratio when new is at most equal to 13%. 
     
     
         3 . The tread according to  claim 1 , wherein the tread comprises several intermediate ribs and edge ribs, the latter axially flanking the intermediate ribs, each intermediate rib being delimited by at least one wavy groove and being provided with a plurality of transverse sipes, and on each intermediate rib:
 the longitudinal length Lm of the contour of the opening of each external cavity onto the tread surface is equal to or greater than an integer multiple N of the pitch Pi of the transverse sipes times an amount at most equal to 25% of this integer multiple N of the pitch Pi,   when new, N+1 transverse sipes of the one same rib open into each open cavity bordering said rib, one of these sipes opening near the end point A of the contour at a distance D 1  from this point A, another sipe opening near the other end point B of the contour at a distance D 2  from this point B, the difference between the two distances D 1  and D 2  being at most equal to 5 mm.   
     
     
         4 . The tread according to  claim 1 , wherein the multiple N is identical for all the intermediate ribs. 
     
     
         5 . The tread according to  claim 1 , wherein the distance D 1  is equal to the distance D 2  for all the ribs. 
     
     
         6 . The tread according to  claim 1 , wherein the open cavities of the wavy grooves are offset from one another so that these external cavities do not come into contact with the road surface at the same time. 
     
     
         7 . The tread according to  claim 1 , wherein the transverse sipes are offset on the intermediate ribs and the open cavities on the wavy grooves in a way suitable for the transverse sipes and these open cavities to come into the contact patch successively. 
     
     
         8 . The tread according to  claim 1 , wherein at least one thin blade of rubbery material is formed at the ends of the contour of the external cavities, each thin blade being attached to at least one of the walls delimiting each external cavity. 
     
     
         9 . The tread for a heavy duty vehicle provided with a tread according to  claim 1 .